BACKGROUND
FIELD
[0001] The present invention relates to image forming apparatuses and process cartridges,
and in particular to image forming apparatuses and process cartridges that include
and serve as imaging devices for forming images in black and for forming images in
other colors, the imaging devices for forming images in black and for other colors
each including a latent image carrier, a charging unit that charges the surface of
the latent image carrier, and a lubricant applying unit that applies lubricant to
the surface of the latent image carrier.
BACKGROUND ART
[0002] Latent image carriers included in imaging devices need to be uniformly charged by
respective charging units so as to have latent images formed thereon. The charging
units each includes a charging member such as a charging wire, a roller, or a brush.
Other examples of the charging member include a non-contact charging member that charges
the surface of the latent image carrier spaced apart therefrom, and a contact charging
member that charges the surface of the latent image carrier being in contact therewith.
Charging biases to be applied to such a charging member also vary, such as a bias
that includes only a direct current (DC) component, and a bias that includes a DC
component and an alternating current (AC) component superposed thereon.
[0003] Charging units employing a charging wire as the charging member are not in contact
with the surfaces of the latent image carriers and employ the DC charging method in
which a charging bias including only a DC component is applied. Such charging units
employing the DC charging method cause no hazard to the surfaces of the latent image
carriers and therefore are advantageous in preventing surface peeling of the latent
image carriers and in extending the lifetimes of the latent image carriers. Moreover,
since such charging units are of the non-contact type, contaminants on the latent
image carriers do not adhere to their charging members. However, there is a problem
in that such charging units tend to generate ozone and nitrogen oxides (NOx) during
charging.
[0004] Examples of a charging member in the form of a charging roller are classified into
the following: a non-contact charging roller type in which the surface of the latent
image carrier is charged without being in contact with the roller, and a contact charging
roller type in which the surface of the latent image carrier is charged while being
in contact with the roller. Non-contact charging rollers apply a charging bias by
the AC + DC charging method in which a DC component and an AC component superposed
thereon are applied. Contact charging rollers apply a charging bias by either the
DC charging method in which only a DC component is applied or the AC + DC charging
method in which a DC component and an AC component superposed thereon are applied.
[0005] Charging units of the non-contact charging roller type generate less ozone and NOx
during charging than charging units of the charging wire type. In addition, contaminants
on the latent image carriers infrequently adhere to the non-contact charging members,
i.e., the charging rollers. However, there is a problem in that superposition of an
AC component is highly hazardous to the surface of each latent image carrier. This
increases the probability of surface peeling of the latent image carrier and thus
shortens the lifetime of the latent image carrier.
[0006] Charging units employing the contact charging roller and the DC charging method have
a simple configuration and are not hazardous to the surfaces of the latent image carriers.
Therefore, such charging units are advantageous in preventing surface peeling of the
latent image carriers and in extending the lifetimes of the latent image carriers.
However, because of direct contact with the latent image carriers, contaminants on
the latent image carriers easily adhere to the surfaces of the respective charging
rollers. The contaminated portion of each charging roller may cause irregular charging
leading to deterioration in image quality. In contrast, charging units employing the
contact charging roller and the AC + DC charging method less frequently cause irregular
charging than charging units employing the contact charging roller and the DC charging
method, even if the charging roller is contaminated, because of the superposition
of an AC component. However, the superposition of an AC component is highly hazardous
to the surface of each latent image carrier. This increases the probability of surface
peeling of the latent image carriers and thus shortens the lifetimes of the latent
image carriers.
[0007] Charging units of imaging devices included in a full-four-color image forming apparatus
have the following characteristics according to their configurations. In the case
where a single imaging device includes a charging wire as the charging member, the
amount of ozone to be generated is smaller than that in the case where all of the
four imaging devices each includes a charging wire. Therefore, emission of ozone from
the inside to the outside of the image forming apparatus can be suppressed. In this
case where a single imaging device includes a charging wire, the amount of NOx to
be generated is also smaller and thus the probability of occurrence of image distortion
is smaller than in the case where all of the four imaging devices each includes a
charging wire. Therefore, adverse influence on images can be suppressed to a negligible
level. On the other hand, when a charging unit employing the contact charging roller
and the DC charging method is applied to an imaging device that forms a black toner
image (hereinafter referred to as an imaging device for black), image irregularity
due to contamination of the charging roller is not noticeable and can be ignored in
practical use. However, when the same charging unit is applied to imaging devices
that form color toner images (hereinafter referred to as imaging devices for color),
image irregularity due to contamination of the charging rollers is noticeable and
may cause a problem in practical use.
[0008] When a charging unit employing the contact or non-contact charging roller and the
AC + DC charging method is applied to imaging devices for color, which are used infrequently,
the short lifetimes of the latent image carriers do not matter very much. However,
when the same charging unit is applied to an imaging device for black, which is used
frequently, the short lifetime of the corresponding latent image carrier may cause
a problem in practical use.
[0009] To summarize, application of charging units having the same configuration to all
of the imaging devices for four colors in a full-color image forming apparatus may
cause problems in practical use. To solve such problems, there are some known image
forming apparatuses in which at least one of a plurality of imaging devices includes
a charging unit having a configuration different from those of the charging units
included in the other imaging devices.
[0010] For example, in an image forming apparatus, a charging unit employing a charging
wire is applied to the imaging device for black, and a charging unit employing a non-contact
charging roller and the AC + DC charging method is applied to the imaging devices
for color. Since only one of the charging units employs a charging wire, emission
of ozone and image distortion caused by NOx are suppressed while the latent image
carrier of the imaging device for black, which is used frequently, can be provided
with a sufficient lifetime. In addition, since the charging unit employing the non-contact
charging roller and the AC + DC charging method is only applied to the imaging devices
for color, which are used infrequently, the problem that the lifetimes of the latent
image carriers may be shortened because of the AC component that is hazardous thereto
is negligible in practical use.
[0011] Moreover, since both charging units are of the non-contact type, contaminants on
the latent image carriers infrequently adhere to the charging rollers. Accordingly,
there is practically no problem due to contamination of the charging rollers.
[0012] Further, when a charging unit employing the contact charging roller and the DC charging
method is applied to an imaging device for black, image irregularity due to contamination
of the corresponding charging roller is not noticeable. Therefore, it is also allowable
that a charging unit employing the contact charging roller and the DC charging method
is applied to the imaging device for black while a charging unit employing the non-contact
charging roller and the AC + DC charging method is applied to the imaging devices
for color. That is, by applying charging units having different configurations to
imaging devices according to the characteristics of the imaging devices, an image
forming apparatus that infrequently has problems in practical use can be realized.
[0013] Under such circumstances, there is a known image forming apparatus in which lubricant
is applied to the surfaces of latent image carriers from the viewpoints of suppressing
surface peeling of the latent image carriers, improving removability of post-transfer
residual toner on the latent image carriers, and preventing strong adhesion of toner
components to the surfaces of the latent image carriers, which is called filming.
[0014] Even in the case where lubricant is applied to the surfaces of the latent image carriers
as described above while charging units of the contact or non-contact charging roller
type are used, a small amount of lubricant may adhere to the charging rollers. Consequently,
irregular charging may occur at some portions of the charging rollers after a certain
period of use, leading to deterioration in image quality.
[0015] Although color image forming apparatuses have become popular in recent years, the
situation where color image forming apparatuses are always used in a full color mode
is not so common yet, practically. Black-and-white images are still used in most cases.
Therefore, among imaging devices for forming images in a plurality of colors, the
imaging device for black has the shortest lifetime. Naturally, users are eagerly demanding
that the lifetime of the imaging device for black be extended. In response to such
a demand, an image forming apparatus including a DC charger in the imaging device
for black and AC + DC charging rollers in the imaging devices for color has been realized
and is becoming popular.
[0016] In such a case, use of a DC charger for black is less hazardous to a photoconductor,
extends the lifetime of a cleaning blade, and reduces the occurrence of failure due
to contamination caused by a lubricant applying unit. This is because the DC charger
is spaced apart farther from the image carrier and therefore is less frequently contaminated
than in the case of an AC + DC charging roller.
[0017] In addition, use of AC + DC charging rollers for color suppresses generation of ozone
and reduces the space, such as an airflow path, necessary for ozone management, leading
to size reduction of the image forming apparatus. Consequently, the imaging device
for black has a longer lifetime than the imaging devices for color. Thus, an image
forming apparatus that matches the current trend in which black-and-white images are
used frequently can be provided.
[0018] Further, use of a DC charger for black is less hazardous to the photoconductor than
use of AC + DC charging rollers for color. Therefore, the amount of lubricant to be
applied by the lubricant applying unit can be reduced. This means that the lubricant
applying unit for black having lubricant of the same amount as those of the lubricant
applying units for color can be used longer than those for color.
[0019] Considering such circumstances, there is another example in which the amounts of
lubricant to be applied by respective lubricant applying units are intentionally made
different for the case for black and the case for color according to the charging
method.
[0020] When different charging methods are employed for the imaging device for black and
the imaging devices for color as described above with the proviso that dedicated process
cartridges, serving as imaging devices, are used respectively for black and for color,
the production cost will be increased.
SUMMARY
[0021] The benefits of the invention are based on a process cartridge according to claim
1 and an image forming apparatus according to claim 10.
[0022] This patent specification describes a novel image forming apparatus includes a plurality
of process cartridges provided for black and for another color. The process cartridges
each including a set of a latent image carrier, a charging unit that charges a surface
of the latent image carrier, and a lubricant applying unit that applies lubricant
to the surface of the latent image carrier. The process cartridges for black and for
the another color each has a cartridge frame with which the process cartridge is attachable
to and removable from an apparatus body. The cartridge frames of the process cartridges
for black and for the another color being of the same type. The process cartridge
for black differs from the process cartridge for the another color in the configuration
of the charging unit. The amounts of lubricant applied by the lubricant applying units
to the respective latent image carriers differ with respect to the configuration of
the charging unit.
[0023] This patent specification further describes a process cartridge used for formation
of an image of black or of another color. The process cartridge includes a set of
a latent image carrier, a charging unit that charges a surface of the latent image
carrier, and a lubricant applying unit that applies lubricant to the surface of the
latent image carrier. The process cartridge has a cartridge frame with which the process
cartridge is attachable to and removable from an apparatus body, the cartridge frame
being of the same type for both cases where the process cartridge is used for black
and the another color. The configuration of the charging unit differs between a case
where the process cartridge is used for black and a case where the process cartridge
is used for the another color, and the amount of lubricant to be applied by the lubricant
applying unit to the latent image carrier differs with respect to the configuration
of the charging unit.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] A more complete appreciation of the invention and many of the advantages thereof
are obtained as the same becomes better understood by reference to the following detailed
description when considered in connection with the accompanying drawings, wherein:
Fig. 1 is a schematic diagram of a color copier serving as an image forming apparatus
according to an exemplary embodiment;
Fig. 2A is a schematic cross-sectional view of a process cartridge for black according
to a first embodiment;
Fig. 2B is a schematic cross-sectional view of a process cartridge for yellow according
to the first embodiment;
Fig. 3 is a plan view showing a lubricant applicator;
Fig. 4 shows springs, one of which is included in the lubricant applicator shown in
Fig. 3;
Fig. 5A is a cross-sectional view of a lubricant applicator according to a second
embodiment in a case where the lubricant applicator is used in a process cartridge
for black;
Fig. 5B is a cross-sectional view of a lubricant applicator according to the second
embodiment in a case where the lubricant applicator is used in a process cartridge
for yellow;
Fig. 6A schematically shows a lubricant applicator according to a third embodiment
in a case where the lubricant applicator is used in a process cartridge for black;
Fig. 6B schematically shows a lubricant applicator according to the third embodiment
in a case where the lubricant applicator is used in a process cartridge for yellow;
Fig. 7A schematically shows a pressing force changer in a case where the pressing
force changer is included in the lubricant applicator shown in Fig. 6A; and
Fig. 7B schematically shows a pressing force changer in a case where the pressing
force changer is included in the lubricant applicator shown in Fig. 6B.
DETAILED DESCRIPTION
[0025] In describing the embodiments illustrated in the drawings, specific terminology is
employed for the purpose of clarity. However, the disclosure of this patent specification
is not intended to be limited to the specific terminology so used, and it is to be
understood that substitutions for each specific element can include any technical
equivalents that operate in a similar manner and achieve a similar result.
[0026] Referring now to the drawings, wherein like reference numerals designate identical
or corresponding parts throughout the several views, a description is given of an
example embodiment.
[0027] An exemplary embodiment in which the invention is applied to a tandem color image
forming apparatus will be described. Fig. 1 is a schematic diagram of a color copier
serving as an image forming apparatus according to the exemplary embodiment. This
copier includes a copier body (hereinafter referred to as a printer section 100),
a paper feed table (hereinafter referred to as a paper feed section 200), a scanner
(hereinafter referred to as a scanner section 300) mounted on the printer section
100, and an automatic document feeder (ADF, hereinafter referred to as a document
feed section 400) mounted on the scanner section 300. The copier also includes a control
section (not shown) that controls operations of the sections included in the copier.
[0028] The printer section 100 includes in its central portion an intermediate transfer
belt 10 as an intermediate transfer member. The intermediate transfer belt 10 is stretched
between a first support roller 14, a second support roller 15, and a third support
roller 16, and is movable therearound clockwise in Fig. 1. Four photoconductors 3K,
Y, M, and C serving as latent image carriers that carry on their surfaces toner images
of black, yellow, magenta, and cyan, respectively, are provided facing the intermediate
transfer belt 10. The photoconductors 3K, Y, M, and C are provided therearound with
chargers 4K, Y, M, and C serving as charging units that uniformly charge the surfaces
of the respective photoconductors 3K, Y, M, and C; developers 5K, Y, M, and C serving
as developing units that develop toner images; and lubricant applicators 6K, Y, M,
and C serving as lubricant applying units that apply lubricant to the surfaces of
the respective photoconductors 3K, Y, M, and C. The lubricant applicators 6K, Y, M,
and C each has a photoconductor cleaning member serving as a cleaner that removes
residual toner on the surface of corresponding one of the photoconductors 3K, Y, M,
and C after a primary transfer.
[0029] The photoconductors 3K, Y, M, and C, the developers 5K, Y, M, and C, the chargers
4K, Y, M, and C, and the lubricant applicators 6K, Y, M, and C constitute imaging
devices 1K, Y, M, and C, respectively, serving as image forming units. The four imaging
devices 1K, Y, M, and C are arranged side by side, thereby constituting a tandem image
forming unit 20. A belt cleaner 17 is provided facing the second support roller 15
with the intermediate transfer belt 10 nipped therebetween. The belt cleaner 17 removes
residual toner on the intermediate transfer belt 10 after a toner image is transferred
onto transfer paper, or a recording medium. The printer section 100 further includes
an exposure unit 21 above the tandem image forming unit 20.
[0030] Primary transfer rollers 8K, Y, M, and C are provided on the inner periphery of the
intermediate transfer belt 10 at positions facing the photoconductors 3K, Y, M, and
C, respectively, with the intermediate transfer belt 10 nipped therebetween. The primary
transfer rollers 8K, Y, M, and C are pressed against the photoconductors 3K, Y, M,
and C with the intermediate transfer belt 10 interposed therebetween, thereby forming
primary transfer parts.
[0031] A secondary transfer unit 29 is provided across the intermediate transfer belt 10
from the tandem image forming unit 20. The secondary transfer unit 29 is constituted
by a secondary transfer roller 22, a secondary-transfer-belt stretching roller 23,
and a secondary transfer belt 24 stretched therebetween. The secondary transfer unit
29 is configured in such a manner that the secondary transfer belt 24 is pressed against
the third support roller 16 with the intermediate transfer belt 10 interposed therebetween
at a position where the secondary transfer roller 22 supports the secondary transfer
belt 24. In this manner, a secondary transfer nip, i.e., a secondary transfer part,
is formed between the secondary transfer belt 24 and the intermediate transfer belt
10.
[0032] A fusing unit 25 that fuses an image transferred onto the transfer paper is provided
on the left side of the secondary transfer unit 29 in Fig. 1. The fusing unit 25 is
constituted by a fusing belt 26, which is an endless belt, and a pressing roller 27
that is pressed against the fusing belt 26. The secondary transfer unit 29 also has
a transfer paper conveying function for conveying to the fusing unit 25 the transfer
paper on which a toner image has been transferred at the secondary transfer nip. The
secondary transfer unit 29 may also include a component such as a transfer roller
or a non-contact charger. In such a case, however, it is difficult to provide the
secondary transfer unit 29 with the transfer paper conveying function.
[0033] A transfer paper reversing unit 28 is provided below the secondary transfer unit
29 and the fusing unit 25, and parallel to the tandem image forming unit 20. The transfer
paper reversing unit 28 reverses the transfer paper so that images can be recorded
on both sides of the transfer paper. With such a configuration, the following operation
can be realized. After an image is fused on one side of the transfer paper, the transfer
paper is redirected by a redirecting tab toward the transfer paper reversing unit
28. The transfer paper is reversed by the transfer paper reversing unit 28 and is
conveyed back to the secondary transfer nip. Then, after a toner image is transferred,
the transfer paper is ejected onto an output tray.
[0034] The scanner section 300 reads image information of a document placed on a contact
glass 32 by using a read sensor 36, and sends the read image information to the control
section.
[0035] In accordance with the image information received from the scanner section 300, the
control section (not shown) causes a laser or a light-emitting diode (LED) (not shown),
for example, included in the exposure unit 21 of the printer section 100 to irradiate
the photoconductors 3 with a laser writing beam L. With this irradiation, electrostatic
latent images are formed on the surfaces of the photoconductors 3. These latent images
are developed into a toner image through a predetermined developing process.
[0036] The paper feed section 200 includes paper feed cassettes 44 provided at different
levels in a paper bank 43, paper feed rollers 42 delivering transfer paper P from
the respective paper feed cassettes 44, separating rollers 45 separating the delivered
transfer paper P piece by piece and sending each piece of the transfer paper P to
a paper feed path 46, conveying rollers 47 conveying the transfer paper P to a paper
feed path 48 in the printer section 100, and so forth.
[0037] The copier of the exemplary embodiment is capable of feeding paper both through the
paper feed section 200 and by hand. The copier includes on its side face a manual
feed tray 51 provided for feeding the paper by hand, a paper feed roller 50 delivering
the transfer paper P from the manual feed tray 51, and separating rollers 52 separating
the delivered transfer paper P piece by piece and sending each piece of transfer paper
P to a manual feed path 53.
[0038] Registration rollers 49 allow only one piece of transfer paper P from one of the
paper feed cassettes 44 or the manual feed tray 51 to be delivered to the secondary
transfer nip provided between the intermediate transfer belt 10, serving as the intermediate
transfer member, and the secondary transfer unit 29.
[0039] In the copier of the exemplary embodiment, to make a copy of a color image, a desired
document is set on a document table 30 of the document feed section 400. Alternatively,
the document feed section 400 is opened, a desired document is set on the contact
glass 32 of the scanner section 300, and the document feed section 400 is closed so
as to press the document.
[0040] Then, by pressing a start switch (not shown), the scanner section 300 is activated
after the document is fed onto the contact glass 32 if the document is set on the
document feed section 400, or immediately if the document is set on the contact glass
32. When the scanner section 300 is activated, a first scanning member 33 and a second
scanning member 34 are moved. The first scanning member 33 emits light from its light
source while receiving the light reflected from the surface of the document and deflecting
the light to the second scanning member 34. The second scanning member 34 reflects
with its mirror the deflected light in such a manner that the light travels through
an image forming lens 35 and enters the read sensor 36. Thus, the image information
of the document is read.
[0041] The chargers 4K, Y, M, and C uniformly charge the surfaces of the respective photoconductors
3K, Y, M, and C. The image information read by the scanner section 300 is subjected
to color separation. The exposure unit 21 performs laser writing on the photoconductors
3K, Y, M, and C in correspondence with their colors. Thus, electrostatic latent images
are formed on the surfaces of the respective photoconductors 3K, Y, M, and C. For
example, image formation in the case of cyan (C) will be described. In conformity
with the electrostatic image formed on the surface of the photoconductor 3C, C toner
is developed by the developer 5C, whereby a monochrome toner image is formed. Likewise,
monochrome toner images for magenta (M), yellow (Y), and black (K) are formed in that
order on the respective photoconductors 3 in the imaging devices 1M, Y, and K. While
the toner images are formed on the respective photoconductors 3, one of the four paper
feed rollers is driven so as to feed a piece of transfer paper of a size matching
the image information.
[0042] At the same time, one of the first support roller 14, the second support roller 15,
and the third support roller 16 is rotatably driven by a driving motor (not shown)
with the other two support rollers being caused to rotate following the driven one,
whereby the intermediate transfer belt 10 is conveyed therearound. While the intermediate
transfer belt 10 is conveyed, the monochrome toner images on the photoconductors 3C,
M, Y, and K are sequentially transferred to the intermediate transfer belt 10, whereby
a composite color image is formed on the intermediate transfer belt 10.
[0043] In the paper feed section 200, one of the paper feed rollers 42 is selectively rotated
and the transfer paper P is delivered from the corresponding one of the paper feed
cassettes 44. The separating rollers 45 separate the transfer paper P piece by piece
and introduce each piece of transfer paper P into the paper feed path 46. The conveying
rollers 47 guide the piece of transfer paper P into the paper feed path 48 in the
printer section 100, which is the copier main body, until the piece of transfer paper
P is stopped at the registration rollers 49. Alternatively, the transfer paper P on
the manual feed tray 51 is delivered by rotating the paper feed roller 50. Then, likewise,
the separating rollers 52 separate the transfer paper P piece by piece and guide each
piece of transfer paper P into the manual feed path 53 until the piece of transfer
paper P is stopped at the registration rollers 49.
[0044] Subsequently, with a timing that matches the conveyance of the intermediate transfer
belt 10 carrying the composite color image, the registration rollers 49 are rotated
and thus the piece of transfer paper P is fed into the secondary transfer nip, which
is the contact part between the intermediate transfer belt 10 and the secondary transfer
roller 22. Then, the composite color image is subjected to secondary transfer under
the influences of, for example, a transfer electric field and a contact pressure produced
at the nip, whereby the color image is recorded on the piece of transfer paper P.
[0045] The piece of transfer paper P that has been subjected to transfer of the color image
at the secondary transfer nip is conveyed to the fusing unit 25 by the secondary transfer
belt 24 of the secondary transfer unit 29. In the fusing unit 25, the color image
is fused with a pressure and a heat applied by the pressing roller 27 and the fusing
belt 26. Then, the piece of transfer paper P is ejected by ejecting rollers 56 and
is stacked on the output tray 57. In the case where images are formed on both sides
of a piece of transfer paper P, the piece of transfer paper P that has been subjected
to fusing of a color image is redirected by the redirecting tab 55, is conveyed to
the transfer paper reversing unit 28, is reversed by the transfer paper reversing
unit 28, and is guided back to the secondary transfer nip, where another image is
recorded on the back surface. Then, the piece of transfer paper P is ejected by the
ejecting rollers 56 onto the output tray 57.
[0046] On the other hand, the belt cleaner 17 removes residual toner on the surface of the
intermediate transfer belt 10 from which the color image has been transferred onto
the piece of transfer paper P at the secondary transfer nip. Thus, the intermediate
transfer belt 10 is prepared for the next image formation performed by the tandem
image forming unit 20.
[0047] Now, process cartridges of the image forming apparatus according to the invention
will be described. Figs. 2A and 2B each shows a process cartridge according to a first
embodiment. Fig. 2A is a schematic cross-sectional view of a process cartridge for
black. Fig. 2B is a schematic cross-sectional view of a process cartridge for yellow.
[0048] First, a process cartridge 500 for black will be described. The process cartridge
500 for black has a frame 510, in which a photoconductor drum 520 serving as an image
carrier, a developer 530, a charger 540, a lubricant applicator 550, and a cleaner
560 are arranged.
[0049] The frame 510 has the same configuration as that of a frame 610 of a process cartridge
600 for yellow described separately below.
[0050] The developer 530 includes stirring rollers 531 and 532 that stir toner, and a magnetic
drum 533 that applies toner to the photoconductor drum 520. The charger 540 includes
a charge wire 541 and employs a DC charging method.
[0051] The lubricant applicator 550 includes a solid lubricant 551, a lubricant applying
member 552, such as a brush drum, that scrapes the solid lubricant 551 and applies
the scraped lubricant to the photoconductor drum 520 while being in contact with both
the solid lubricant 551 and the photoconductor drum 520, a spring 553 serving as a
pressing member that presses the solid lubricant 551 against the lubricant applying
member 552, and an application blade 554 that evenly spreads the applied lubricant.
The spring 553 is provided in a number of two in the longitudinal direction of the
lubricant applying member 552. As described separately below, the spring 553 included
in the lubricant applicator 550 has a pressing force smaller than that of a spring
653 included in a lubricant applicator 650 of the process cartridge 600 for yellow.
Thus, even in the case where the same lubricant is used in all of the lubricant applicators,
the process cartridge 500 for black can have a longer lifetime than those of the process
cartridges for color including yellow.
[0052] The cleaner 560 includes a cleaning blade 561 that collects toner while being in
contact with the photoconductor drum 520, a cleaning brush 562 that is rotatably in
contact with the photoconductor drum 520, and a conveying screw 563 that conveys the
collected toner.
[0053] To summarize, the process cartridge 500 for black includes the charger 540 employing
a DC charging method and provides long lifetimes with the lubricant applicator, the
image carrier, and the cleaning blade, because of the reduced amount of the lubricant
to be applied. Since process cartridges for black are frequently used, such extension
of component lifetimes can satisfy the demand of users.
[0054] Next, process cartridges for color, i.e., Y; M; and C, in particular the process
cartridge 600 for yellow, will be described. The process cartridge 600 for yellow
has the frame 610 that has the same configuration as that of the frame 510 of the
process cartridge 500 for black. In the frame 610, a photoconductor drum 620 serving
as an image carrier, a developer 630, a charger 640, the lubricant applicator 650,
and a cleaner 660 are arranged.
[0055] As described above, the frame 610 has the same configuration as that of the frame
510 of the process cartridge 500 for black. In other words, the process cartridge
500 for black and the process cartridge 600 for yellow can be provided with frames
of the same type. Hence, there is no need to prepare separate frames dedicated respectively
for black and for color. Consequently, commonality of the frame in terms of the mold,
production line, and component management can be realized. This is advantageous in
cost reduction.
[0056] The developer 630 includes stirring rollers 631 and 632 that stir toner, and a magnetic
drum 633 that applies toner to the photoconductor drum 620. The charger 640 includes
a charging roller 641 and employs an AC + DC charging method.
[0057] In the process cartridge 600 for yellow, since the charger 640 employs the AC + DC
charging method, emission of ozone can be reduced. Accordingly, the ozone management
mechanism can be simplified, whereby the cartridge size can be reduced.
[0058] The lubricant applicator 650 includes a solid lubricant 651, a lubricant applying
member 652, such as a brush drum, that scrapes the solid lubricant 651 and applies
the scraped lubricant to the photoconductor drum 620 while being in contact with both
the solid lubricant 651 and the photoconductor drum 620, the spring 653 serving as
a pressing member that presses the solid lubricant 651 against the lubricant applying
member 652, and an application blade 654 that evenly spreads the applied lubricant.
As described above, the lubricant applicator 650 has the same configuration as that
of the lubricant applicator 550 included in the process cartridge 500 for black, except
that the spring 653 has a pressing force larger than that of the spring 553. The spring
653 is provided in a number of two in the longitudinal direction of the lubricant
applying member 652 (see Fig. 4).
[0059] The lubricant applicator 650 has a configuration similar to that of the lubricant
applicator 550 included in the process cartridge 500 for black. In the first embodiment,
the lubricant applicator 550 of the process cartridge 500 for black and the lubricant
applicator 650 of the process cartridge 600 for yellow include the spring 553 and
the spring 653, respectively, having different pressing forces, as described separately
below.
[0060] The cleaner 660 includes a cleaning blade 661 that collects toner while being in
contact with the photoconductor drum 620, a cleaning brush 662 that is rotatably in
contact with the photoconductor drum 620, and a conveying screw 663 that conveys the
collected toner.
[0061] Next, the lubricant applicators 550 and 650 will be described. Fig. 3 is a plan view
showing a lubricant applicator. Fig. 4 shows springs, one of which is included in
the lubricant applicator shown in Fig. 3. In the first embodiment, the lubricant applicators
550 and 650 have the same configuration, as shown in Fig. 3, except that the springs
553 and 653 have different pressing forces. Referring to Fig. 3, the solid lubricant
551 or 651 in the lubricant applicator 550 or 650 has almost the same length as that
of the photoconductor drum 520 or 620. To uniformly press the solid lubricant 551
or 651 against the lubricant applying member 552 or 652, the spring 553 or 653 is
provided in a number of two. Further, in the first embodiment, to make the amount
of lubricant to be applied by the lubricant applicator 550 in the process cartridge
500 for black smaller than that in the process cartridge 600 for yellow, the spring
553 of the process cartridge 500 for black is formed with a length L1, and the spring
653 of the process cartridge 600 for yellow, an example of the process cartridges
for color, is formed with a length L2. That is, the springs 553 and 653 of two different
kinds are prepared so that either of the two can be selected in accordance with the
type of the lubricant applicator to be used, i.e., the lubricant applicator 550 or
650.
[0062] The springs selected for the lubricant applicators 550 and 650 are respectively mounted
therein by being compressed so as to have the same length, whereby the pressing force
of the spring 553 of the process cartridge 500 for black is made smaller than that
of the spring 653 of the process cartridge 600 for yellow. In addition, it is desirable
that the surface of the spring 553 to be used in the process cartridge 500 for black
and the surface of the spring 653 to be used in the process cartridge 600 for yellow
be colored differently. With such different surface colors of the springs, the different
kinds of springs can be distinguished from each other easily.
[0063] This way of coloring also contributes to distinguishing between various imaging devices
(in a state of not having chargers mounted thereon) for black and for color in the
manufacturing process, whereby confusion can be prevented and maintenance in the market
can be provided efficiently. An exemplary accident that can be prevented is as follows.
An AC + DC charging roller for color is mistakenly set in a process cartridge having
a lubricant applicator with a setting of the pressing force for black, and therefore
a problem such as filming due to insufficient amount of the lubricant applied to the
image carrier occurs. It should be noted that the pressing forces of the springs 553
and 653 can be changed not only by changing their length but also by changing any
of their other settings, such as the spring wire diameter and the number of turns
on the spring.
[0064] Further, in the first embodiment, frames 555 and 655, on which the springs 553 and
653 are mounted respectively, have observation windows 556 and 656, respectively.
Through these observation windows 556 and 656, an operator can distinguish with the
eye E the types of the springs 553 and 653 disposed in the lubricant applicators 550
and 650 by their colors. As an alternative for enabling observation of the spring
with the eye, a transparent closed frame or an open frame covered with a transparent
member may be used.
[0065] Next, a second embodiment of the invention will be described. Figs. 5A and 5B are
cross-sectional views of a lubricant applicator according to the second embodiment.
Fig. 5A shows a case where the lubricant applicator is used in a process cartridge
for black. Fig. 5B shows a case where the lubricant applicator is used in a process
cartridge for yellow.
[0066] In the second embodiment, the process cartridge 500 for black and the process cartridge
600 for yellow, an example of the process cartridges for color, each includes the
same pressing member, a spring 710. In the second embodiment, the spring 710 is set
to a frame 720 with an adjustment member 730. As shown in Figs. 5A and 5B, the adjustment
member 730 is a plate-like member having a concave portion, which is a fitting portion
740. By changing the orientation of the fitting portion 740 when mounting the spring
710 on the frame 720, the length of the spring 710 can be changed.
[0067] In the second embodiment, to mount the lubricant applicator in the process cartridge
500 for black, the adjustment member 730 is attached to the frame 720 in such a manner
that the fitting portion 740 projects away from a solid lubricant 750 as shown in
Fig. 5A. In this case, the spring 710 disposed between the solid lubricant 750 and
the adjustment member 730 has a length M1.
[0068] In contrast, to mount the lubricant applicator in the process cartridge 600 for yellow,
the adjustment member 730 is attached to the frame 720 in such a manner that the fitting
portion 740 projects toward the solid lubricant 750 as shown in Fig. 5B. In this case,
the spring 710 disposed between the solid lubricant 750 and the adjustment member
730 has a length M2.
[0069] Here, since M1 is larger than M2, the tension of the spring 710 is lower in the case
where it is used in the process cartridge 500 for black than in the case where it
is used in the process cartridge 600 for yellow.
[0070] With such a configuration, the pressing force applied to the solid lubricant 750
by using the same spring 710 can be changed appropriately for the process cartridge
500 for black and for the process cartridge 600 for yellow.
[0071] In the second embodiment, by checking the orientation of the fitting portion 740
of the adjustment member 730, process cartridges can be easily distinguished between
those for black and those for color. Moreover, all the process cartridges can have
identical components except for the charger.
[0072] Next, a third embodiment will be described. Figs. 6A and 6B schematically show lubricant
applicators according to the third embodiment. Figs. 7A and 7B schematically show
pressing force changers included in the lubricant applicator shown in Figs. 6A and
6B, respectively. Figs. 6A and 7A each shows a case where the lubricant applicator
is used in a process cartridge for black. Figs. 6B and 7B each shows a case where
the lubricant applicator is used in a process cartridge for yellow.
[0073] In the third embodiment, two cams 810 (only one of the two is shown in Figs. 6A and
6B) are disposed on a solid lubricant 840 at equal distances from the center of the
solid lubricant 840. The cams 810 are each provided in a rotatable state with a shaft
820. A spring 830 is stretched between the cams 810 in such a manner as to urge the
cams 810 in a direction in which the cams 810 press the solid lubricant 840. Further,
the two shafts 820 are provided with a common pressing force changer 900 that changes
the distance between the shafts 820.
[0074] Referring to Figs. 7A and 7B, the pressing force changer 900 includes a rotary knob
910 and two arms 920. The arms 920 each has one end thereof being rotatably fastened
to the rotary knob 910 with a pin 911, and the other end thereof being rotatably fastened
to the shaft 820. Each of the shafts 820 is provided with a slider 930. When the rotary
knob 910 is rotated, the shafts 820 move with the guide of the respective sliders
930, whereby the distance between the shafts 820 can be changed.
[0075] The rotary knob 910 has an indication member 912 that indicates the angle of rotation
of the rotary knob 910. When the lubricant applicator is mounted in the process cartridge
500 for black, the rotary knob 910 is set in an orientation shown in Fig. 7A. In this
case, the distance between the shafts 820 is a distance N1. When the lubricant applicator
is mounted in the process cartridge 600 for yellow, an example of the process cartridges
for color, the rotary knob 910 is set in an orientation shown in Fig. 7B. In this
case, the distance between the shafts 820 is a distance N2. Here, since N1 is smaller
than N2, the tension of the spring 830 (shown in two-dot chain lines in Figs. 7A and
7B) is lower in the case where it is used in the process cartridge 500 for black in
the case where it is used in the process cartridge 600 for yellow.
[0076] In the third embodiment, pressing forces equal to each other are applied to the solid
lubricant 840 at two positions by the use of two cams 810. Therefore, the solid lubricant
840 is pressed uniformly against the lubricant applying member. In addition, the pressing
force applied to the solid lubricant 840 can be identified by visually checking the
orientation of the indication member 912 of the rotary knob 910. Therefore, it is
easy to identify whether the pressing force changer 900 is set for the process cartridge
500 for black or for the process cartridge 600 for yellow.
[0077] The above-described embodiments are illustrative and do not limit the present invention.
Thus, numerous additional modifications and variations are possible in light of the
above teachings. For example, elements at least one of features of different illustrative
and exemplary embodiments herein may be combined with each other at least one of substituted
for each other within the scope of this disclosure and appended claims. Further, features
of components of the embodiments, such as the number, the position, and the shape,
are not limited the embodiments and thus may be set as preferred. It is therefore
to be understood that, within the scope of the appended claims, the disclosure of
this patent specification may be practiced otherwise than as specifically described
herein.
1. A process cartridge for forming of an image of black or of another color, the process
cartridge comprising:
a set of a latent image carrier;
a charging unit configured to charge a surface of the latent image carrier; and
a lubricant applying unit configured to apply lubricant to the surface of the latent
image carrier,
wherein the process cartridge has a cartridge frame with which the process cartridge
is attachable to and removable from an apparatus body, the cartridge frame being of
the same type for both cases where the process cartridge is used for black and the
another color, and
wherein the configuration of the charging unit differs between a case where the process
cartridge is used for black and a case where the process cartridge is used for the
another color, and the amount of lubricant to be applied by the lubricant applying
unit to the latent image carrier differs with respect to the configuration of the
charging unit.
2. The process cartridge according to Claim 1,
wherein the lubricant applying unit includes a solid lubricant, an applying member
that scrapes the solid lubricant and applies the scraped lubricant to the latent image
carrier while being in contact with both the solid lubricant and the latent image
carrier, and a pressing mechanism that presses the solid lubricant against the applying
member, and
wherein the lubricant applying unit changes the amount of lubricant to be applied
to the latent image carrier by changing the pressing force of the pressing mechanism.
3. The process cartridge according to Claim 2, wherein the pressing mechanism presses
the solid lubricant at a plurality of positions on the solid lubricant.
4. The process cartridge according to Claim 2,
wherein the pressing mechanism includes a plurality of springs that press the solid
lubricant, and
wherein the springs are selected from springs of different types prepared with pressing
forces that differ with respect to the type.
5. The process cartridge according to Claim 4, wherein the springs of different types
have surface colors that differ with respect to the type.
6. The process cartridge according to Claim 4, wherein the lubricant applying unit is
configured in such a manner that the springs disposed therein are observable from
the outside.
7. The process cartridge according to Claim 2,
wherein the pressing mechanism includes a spring that presses the solid lubricant
and a holding member that holds the base of the spring, and
wherein the holding member has a shape capable of producing two initial lengths, long
and short, of the spring by changing the orientation of the holding member, the orientation
of the holding member being selected in accordance with the amount of lubricant to
be applied.
8. The process cartridge according to Claim 2,
wherein the pressing mechanism includes
two cams rotatably supported by respective shafts and disposed in such a manner as
to be spaced apart from each other while being each in contact at one end thereof
with the solid lubricant;
a spring stretched between the cams and urging the cams in a direction in which the
cams rotate so as to press the solid lubricant; and
a pressing force changer that changes the pressing force applied to the solid lubricant
by the cams with the use of the spring, the pressing force being changeable by changing
the distance between the shafts supporting the cams.
9. The process cartridge according to Claim 8, wherein the pressing force changer includes
a knob whose orientation is changeable manually and a link that changes the distance
between the shafts when the orientation of the knob is changed.
10. An image forming apparatus comprising:
a plurality of process cartridges provided for black and for another color, the process
cartridges, each comprising the features of at least one of claims 1 to 9, and therefore
including
a set of a latent image carrier;
a charging unit configured to charge a surface of the latent image carrier; and
a lubricant applying unit configured to apply lubricant to the surface of the latent
image carrier,
wherein the process cartridges for black and for the another color each having a cartridge
frame with which the process cartridge is attachable to and removable from an apparatus
body, and the cartridge frames of the process cartridges for black and for the another
color being of the same type, and
wherein the process cartridge for black differs from the process cartridge for the
another color in the configuration of the charging unit, and the amounts of lubricant
applied by the lubricant applying units to the respective latent image carriers differ
with respect to the configuration of the charging unit.